1. Field of the Invention
The invention relates to a device for applying formatted adhesive applications on a transfer roller, which delivers through a process of rolling off its adhesive applications to workpieces, which are fed continuously for the purpose of covering with adhesive.
2. Description of the Related Art
Such adhesive applicators already exist in various embodiments. They usually consist (see, for example DE 196 34 594 A1) of one or two adhesive rollers, which are positioned at the opening edges of a housing, enveloping an adhesive chamber, and close said housing and which deliver their adhesive applications to a transfer roller. Almost the entire area of the transfer roller can be provided with adhesive applications; or the transfer roller can be provided with blocks, which receive and transfer the formatted adhesive applications as a function of their shape. The drawback of such prior art adhesive applicators lies in the fact that, as the format(s) of the adhesive applications change(s), the transfer roller bearing the blocks must also be changed. Furthermore, with the prior art adhesive applicators the adhesive cannot be prevented from escaping continuously from said adhesive applicators so that the adhesive has to be collected and drained off or recirculated. Furthermore, it is necessary to clean the prior art adhesive applicators regularly, a process that is quite time consuming.
Therefore, the object of the invention is to provide an adhesive applicator of the class described in the introductory part that makes it possible to modify the adhesive formats easily and quickly; and its simple design eliminates the need to clean, since it works in a virtually maintenance free manner.
The invention solves this problem in that, in addition to the transfer roller, there are adhesive nozzles that are spaced axially equidistant apart and are aimed against the jacket of the transfer roller and are provided with valves whose opening and closing times are controlled individually by a controller.
With the adhesive applicator of the invention arbitrary formats of adhesive applications can be sprayed on the transfer roller through suitable control of the adhesive nozzles. If the device is adjusted in such a manner that all of the sprayed on adhesive applications are delivered from the transfer roller to the workpieces, then it is possible to operate the device more cleanly and virtually maintenance free.
It is possible for adhesive applicator nozzles, which are arranged side by side, not to apply a continuous adhesive application, thus an adhesive application, which does not comprise parallel strips, even if the strip shaped adhesive applications that are sprayed on the transfer roller are spread out, during the transfer process, on the workpieces to be covered with glue, for example a web that is travelling by. Therefore, another embodiment of the invention provides that a row of adhesive nozzles is mounted on a support, which moves the row parallel to the axis of the transfer roller by means of a controller. In so doing, the adhesive nozzles can be controlled in such a manner as a function of the format to be generated on the transfer roller that during each revolution each of the adhesive nozzles used for the format to be produced applies a circumferential strip of the required length on the transfer roller; and during the next revolution an adjustment in the axial direction takes place in such a manner that the next adhesive application is applied between the previously produced adhesive applications. In this operating mode it can be assumed that in each cycle the transfer roller delivers only a part of the adhesive strips to be sprayed on to the passing web or the passing workpieces so that the adhesive is always transferred over the entire area in accordance with the formats.
It is advantageous for the adhesive nozzles to be spaced so far apart from each other that the distance is equivalent to twice the width of the adhesive track to be applied by the same. Hence the adhesive nozzles can be slid back and forth by the width of one adhesive track in time with one revolution of the transfer roller. In this operating mode each adhesive track is applied only in every second revolution of transfer roller so that, as a function of the number of adhesive nozzles in operation and the circumferential lengths of the adhesive tracks to be produced through suitable control, any arbitrary size of adhesive applications to be applied over the whole area can be applied on the transfer roller.
The arrangement of suitably spaced adhesive nozzles also accounts for the circumstance that the adhesive nozzles are very expensive so that even for the purpose of applying adhesive over the entire area in accordance with a specific format only an equivalently reduced number of adhesive nozzles is necessary.
If at the start of the operation no waste is to be produced in such a manner that the first application is not over the entire area but only in strips, the control can take place in such a manner that two revolutions of the transfer roller result in an application of adhesive that covers the entire area according to the format before said adhesive application is received by the passing webs or workpieces.
It is also possible to apply adhesive applications over the whole area by means of another strip pattern. For this reason another embodiment provides that the adhesive nozzles are spaced apart multiple times the width of the adhesive tracks to be applied by said adhesive nozzles and can be moved forward by the width of one adhesive track in a number of these multiple corresponding steps in time with the revolutions of the transferroller and preferably back again in one step.
It is advantageous for the control of the adhesive nozzles to comprise a microcomputer controller. The images of the formatted adhesive applications can be put into a storage (bit map) of an appropriate computer, which controls the opening and closing times of the adhesive applicator nozzles for the purpose of applying adhesive according to a specific format.
A preferred embodiment of the invention provides that the adhesive nozzles are mounted on an elongated support, which can be moved step by step in any direction in time with the revolution of the transfer roller in guides of the machine frame by means of a driver, e.g. a pressure medium piston cylinder unit. With this sliding unit the pattern of the adhesive tracks to be produced during successive revolutions can be controlled.